Someone created a similar extension for chrome called little rat[0], it needs to be installed in developer mode bec chrome doesn’t allow extensions to interact with each normally.
I was using a similar extension which whitelisted / blacklisted IP addresses in Chrome. I had it set to blacklist my home IP, which I paired with an in-browser VPN app. Since Chrome's latest extension update (about 3 weeks now?), I've had Chrome send requests to pages which were open before the extension loaded, leaking my IP. I assume similar issues could happen extension-to-extension, so this shouldn't be used for any privacy-related reasons - can't trust a Chrome extension to block 100% of anything.